Air conditioning apparatus



March 2:, 1941. I E R, wo -r 2,236,190

AIR CONDITIONING APPARATUS Filed Feb. 6, 1955 STHRTINQ RELRY *"STRRTING RELHY COLDEST/ TUBES f WITNESSES: f INVENTOR 7g W e Enwnnp Ewen-s 1 Patented Mar. 25, 1941 PATENT OFFICE azsaisc AIR coum'rrome APPARATUS Edward R. Wolfert, Wilkinsburg, Pa., asslgnor to Westinghouse Electric &=Manufactnring Com- Pany, East Pittsburgh,

Pennsylvania Pa., a corporation of Application February 6, 1935, Serial No. 5,211

13 Claims.

My invention relates to air conditioning appar'atus, more particularly to air cooling and dehumidifying apparatus,- and it has for an object to provide improved apparatus.

The present invention is more particularly applicable to air cooling apparatus, such as a unit or room cooler, comprising a cooling coil disposed in a casing or a cabinet and means for circulating air through the casing in contact with the V cooling coil and into the room.-

In the ordinary room cooler, the cooling action is initiated and terminated in response to dry bulb temperature in the room, to maintain the same substantially constant. The temperature of the cooling coil is substantially constant and is chosen to be ordinarily below the dew point so as to efiect dehumidification as well .as cooling. However, the amount of deh'umidification under varying conditions is not controlled but is only such as accompanies the cooling action required to obtain the desired dry bulb temperature.

It is an object of my invention to vary the operation of the apparatusso as to control the humidity as well as the temperature of the conditioned enclosure.

In accordance with my invention, I provide a passage extending from the discharge or downstream side of the cooling coil and circulating fan to the inlet or upstream side thereof, whereby a portion of the air that has passed over the coil is again passed over the coil to provide a greater degree of dehumidi-flcation. .By recirculating a portion of the air which has. been discharged from the coil, the volume of air delivered to the enclosure is reduced, but such reduced volume of air is cooled to a lower temperature and, therefore, dehumidified to a. greater degree. In one embodiment of the invention, the recirculated air is mixed with the air conveyed to the coil for cooling and dehumidification, so that the temperature of the air received at the inlet side of the coil is reduced. This lower temperature results in reduced suction pressure and temperature of the refrigerant in the coil; so that the air is cooled to a lower temperature.

In a second embodiment of the invention, a portion of the air that has passed over one part of the coil is returned to the inlet side of the coil and passes over a second'part of the coil for further dehumidifl-cation. In its first passage over the coil, most of the superheat or sensible heat above the dew point is removed, so that the air is discharged in substantially saturated condition. Thus, in its second passage over the coil, a greater amount of dehumidiiicatiou is eifected. By

controlling recirculation of air over the second Part of the coil, the amount of dehumidification eifected may be varied.

In accordance with a further feature of my invention, I provide a control system whereby operation of the cooling coil. is effected and flow through said passage is shut ofi independently of the humidity in the enclosure when the temperature is above a predetermined value, and whereby iiow through said passage and operation of the cooling coil are efiected in response to high humidity when the temperature is below said predetermined value. Provision may also be made for terminating cooling action when the temperature reaches a minimum value of comfortable temperature.

The above and other objects are effected by my invention as will .be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a diagrammatic view of one embodi ment of air conditioning apparatus and a 'control system therefor;

Fig. 2 is a wiring diagram of a modified form of control system; and

Fig. 3 shows another embodiment of air conditioning apparatus and a control system suitable therefor.

Referring to the drawing in detail, I show a duct or casing l having a cooling element ll disposed therein to contact with the air flowing through the duct. The cooling element is preferably in the form of a cross finned coil. A fan I! driven by a motor 13 is provided for effecting flow of air from a return air inlet I4 and an outside air inlet l5, over the coil II, and for discharging the same through an outlet ii to the space to be. air conditioned. Dampers I! may be provided in the air inlets for controlling the flow of air therethrough. Y

In accordance with the present invention, I provide a passage l8 communicating at one end with the duct l0 at a point beyond or on the downstream side of the coil II and communicating at its other end with the duct on the uppansion valve 21, which is preferably of the type known as a thermostatic expansion valve, for controlling the admission of refrigerant to the coil or evaporator Such a valve controls the flow of refrigerant in accordance with the capacity of the cooling coil to evaporate refrigerant, and permits the pressure and temperature of vaporization to vary with the wet bulb temperature or total heat of the air passing over the coil The control system includes a thermostat T1 for maintaining the'en-closure at the desired temperature. The thermostat T1 has a switch 28 which is closed when the temperature rises above said temperature and opens when the temperature has been reduced to a slightly lower value, and it also has a switch 29 which operates in the reverse direction. A humidostat H has contacts 3| which close in response to a predetermined high value of a humidity condition, such as rela- 5 tive humidity, and which opens in response to a slightly lower value. If desired, a humidos-tat responding to wet bulb temperature or dew point may be .used. A low limit thermostat T2 may also be provided, and has a switch 32 adapted to Open in the event that the temperature reaches an uncomfortably low value. The thermostats T1 and T2 and the humidostat H are subjected to the air in the enclosure or space to be air conditioned, being disposed either in the enclosure or in the return air inlet I4, so as to respond to the temperature and humidity thereof.

The circuits for the solenoid 22 and the starting relay of the motor 24 extend in common from a line conductor L1, through one pole of a cooling switch 33 to a conductor 34, the latter being connected to one terminal of the switch 28 and one terminal of the switch 3|. The other ter minal of the switch 3| is connected to one terminal of the switch 32, The other terminals of the switches 28 and 32 are connected to a conductor 35. It will be noted that the switches 3| and 32 are in series with each other and in parallel with the switch 28. From the conductor 35, the circuit 36 for the motor starting relay extends through said relay to a line conductorLz. A circuit 31 for the solenoid 22 extends from the conductor 35 through the switch 29 and the solenoid 22 to the line conductor L2. A circuit 38 for the fan motor I3 is connected to line conductor L1 through the other pole of the switch 33 and also by a fan switch 39 in parallel therewith, and it is also connected to the line conductor L2.

The operation of this embodiment is as follows: To effect cooling and dehumidifying operation of the apparatus, it is necessary first to close the switch 33, which eiiects continuous operation of the air circulating fan I2 and which enables operation of the cooling coil and of the damper l9 under automatic control. perature in the enclosure is above the value desired to be maintained therein, the thermostat T1 closes the switch 28 and opens the switch 29. The circuit for the motor starting relay is completed, thereby causing the motor 24 to drive the compressor 23 for effecting refrigerating action. The switch 29 opens the circuit 31 to the solenoid 22 so that the spring 2| closes the damper l9. Air is now circulated over the cooling coil without recirculation of air through the passage |8. The maximum amount ofair is discharged through the outlet IE to the enclosure, the cooling action being utilized in this case to effect the maximum amount of reduction in dry If the tembulb temperature, although some dehumidification is effected unless the humidity is very low. While the thermostat T1 calls for cooling, the humidostat H cannot eflect'recirculation.

When the temperature in the enclosure has been brought down to the desired value, the thermostat T1 opens the switch 28 and closes the switch 29, placing the solenoid circuit 31 in condition to be closed by the humidostat switch 3|. If the humidity in the enclosure is high, the humidostat H closes the switch 3|, thereby closing both the starting relay circuit 36 and the solenoid circuit 31 through the switches 3| and 32. Energization of the solenoid 22 opens the damper l9 so that a portion of the air which has passed over the cooling coil and is in substantially saturated condition passes to the suction side of the fan I2, and is recirculated over the cooling coil to provide a greater degree of dehumidification. In the embodiment of Fig. 1, this air is mixed with the warmer air from the inlets l4 and I5, to provide a mixture of lower temperature than the air from the inlets l4 and I5, 50 that the cooling coil operates at lower suction pressure and temperature to eiiect a lower temperature of the discharged air. Thus, with the damper I9 open, a smaller quantity of air is delivered to the enclosure but it is at a lower temperature and consequently of lower absolute humidity, so that a greater portion of the cooling action of the coil H is used for dehumidification of air for the enclosure and a smaller portion for dry bulb temperature reduction.

While the apparatus is operating with the damper I!) open as described for dehumidification, the sensible heat cooling or dry bulb temperature reduction is less than the ordinary heat leakage, so that the temperature ordinarily will not be reduced to any great extent below that maintained by the thermostat T1, but it will increase the intervals between operation -of the thermostat T1 calling for cooling. If and when the thermostat T1 does operate to call for cooling before sufficient operation with recirculation fordehumidification has been effected, the opening of the switch 29 effects closing of the damper I9 so that the apparatus operates for maximum temperature reduction until the desired tempera.- ture is again reached,

If the amount of sensible heat cooling effected with the damper l9 open is substantially in excess of the sensible heat load of the enclosure, as on a day which is very humid but not very hot, the temperature in the enclosure may tend to drop to an uncomfortably low value. The thermostat T2 responds to such temperature drop by operating the switch 32 to open the starting relayand solenoid circuits to discontinue further cooling. I

It will be noted that, as soon as operation for maximum dehumidification under control of humidostat H is completed, the damper I9 is closed its switch 3| in response to high humidity. as in Fig. 1. A thermostat T4, which opens a switch 42 in response toa higher temperature indicating that the temperature in the enclosure cannot be held down to a sufliciently low value while the damper is opened, may be provided. The starting relay and solenoid circuits extend in common from the line conductor L1, through one pole of the cooling switch 33 to the conductor 34, as in Fig. 1. One terminal of the switch 4| is connected to the conductor 34 and the other terminal to a conductor 43. The terminals of the starting relay are connected to the conductor 43 and the line conductor L2, respectively. A solenoid circuit extends from the conductor 43 through the switches 42 and 3| in series and through the solenoid 22 to the line conductor L2.

The .thermostat Ta closes the switch 4| to effect cooling action whenever the temperature of the enclosureis above the desired value, and opens the switch 4| to terminate cooling action whenever the temperature is below said value. While the refrigerating-mechanism is in operation, if the humidity in the enclosure is above the desired value and the temperature is not excessively high, the switches 3| and 42 are closed to energize the solenoid 22 and open the damper l9. Recirculation of cooled air is then eflected for greater dehumidiflcation as already described. If the sensible heat cooling that accompanies operation with the damper I! open is insuilleient to prevent an excessively high temperature, then the thermostat T4 opens the switch 42 to close the damper IS. The apparatus then operates toeffect maximum sensible heat cooling and minimum dehumidiflcation-until the temperature is brought down to a somewhat lower temperature to permit the switch 42 to close. It will be noted that, in this embodiment, operation with recirculation has preference when the temperature is within limits of comfortable temperature, but that operation without recirculation is effected when the temperature becomes excessive. It will also be notedthat operation with recirculation cannot be efiected except when the main thermostat T: calls for cooling.

In Fig. '3, I show an embodiment of my invent ion in which the recirculated air may be kept separate from the main stream of warm air, and in which varying quantities of air may be recirculated. A partition 44 divides the tubes of a cooling coil or element Ila into .two groups, Mb

and He, the latter being disposed adjacent the outlet of the passage I3, and comprising the coldpivot I9b from the position shown in whichmaximum quantity of cold air from the passage- II is recirculated, through intermediate positions, in which decreasing quantities of cold air and increasing quantities of warm air are admitted to the tubes llc, to the position closing the outlet of passage I! in which case no air is recirculated and only warm air passes over the tubes llc. In this embodiment, a circulating fan I241 is disposed on the outlet or downstream side of.

the cooling element to permit separate air streams.

The damper l9a is actuated by a wet bulb thermostat 45 which may comprise an expansible chamber 46 covered by an absorbent material 41 that is kept in moist condition, and which is subjected to the air in the enclosure being conditioned. As the wet bulb temperature of the crank or lever No, a connecting rod I 9d and a lever ISe pivoted to a fulcrum l9 as will be quite apparent from Figure 3;

A thermostat T5, which maintains the desired dry bulb temperature of the conditioned enclosure, actuates a switch 49 in the circuit of the compressor motor starting relay, as in the previous embodiments. A solenoid 52 is provided for operating the damper |9a to close the passage l8 when cooling action is terminated. It is actuated by a circuit 53, which extends from the line conductorLi, through the switch 39 or the pole of the switch 33 that controls the fan circuit 38,

through the contacts 54 of a relay 55 and through The the solenoid 52 to the line conductor'Lz. winding of the relay 55 is connected in the starting relay circuit 5| and arranged to open the contacts 54 when energized.

In the operation of the embodiment shown in Fig. 3,the switch 33 must be closed to permit cooling operation. The thermostat {1'5 responds to a predetermined maximum temperature by closing the circuit 5| to start cooling action and opens the switch in response to a slightly lower temperature to terminate cooling action. While cooling action is eifected, the damper I9a is operated by the Wet bulb thermostat 45 to regulate the quantity of recirculated air. As the wet bulb temperature increases, the damper |9a increases the quantity of air that is recirculated, so that greater dehumidification is eifected. In this case, the recirculated air is conveyed over the colder tubes He in order to reduce the temperature thereof to a lower degree and thereby to effect maximum dehumidification. The recooled air from the tubes H0 is mixed with the once cooled air from the tubes ||b by the fan [2a and a portion of the mixture is conveyed by the passage I. to the tubes llc. As the wet bulb temperature decreases-the damper |9a decreases the quantity of recirculated air permitting a greater quantity of warm air to pass to the tubes llc. As soon as cooling action is terminated, the winding of the relay 55 is deenergized to close the contacts 54. If the fan |2a is operating, the circuit 53 is closed to energize the solenoid 52, so

that the damper I911 is moved to the extreme the fan l2a for ventilation is provided.

'In speaking of recirculation of cooled and dehumidified air over the cooling element, I mean, of course, recirculation of the air before it is delivered to the air conditioned enclosure.

From the above description; it will be seen that I have provided relatively simple and-inexpensive air conditioning apparatus, particularly suitable for unit conditioners and small installations, in which the humidity as well as the temperature may be regulated to maintain the same within comfortable limits.

While I have shown my invention in three forms, it will be obvious to those skilled in the art that it is not so limited, bllt'is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitation shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In apparatus for air conditioning an enclosure, the combination of a surface cooling element for cooling air and reducing the moisture content thereof, fluid translating means for ef- Y fecting flow of air to be conditioned over said cooling element, means for conveying air from said cooling element to said enclosure, means for selectively withdrawing aportion of the cooled air from said conveying means and recirculating the same over said cooling element, whereby the apparatus may be operated either without recirculation to effect primarily temperature reducti'on of the air delivered to the enclosure or with recirculation to effect maximum reduction in moisture content thereof, and means for controlling the second-mentioned operation in response to a humidity condition of the air in the enclosure.

2. In apparatus for air conditioning an enclosure, the combination of a surface cooling element for cooling air and reducing the moisture content thereof, fluid translating means for effecting flow of air to be conditioned over said cooling element, means for conveying'air from said cooling element to said enclosure, means for selectively withdrawing a portion of the cooled air from said conveying means and recirculating the same over said cooling element, whereby the apparatus may be operated either without recirculation to effect primarily temperature reduction or with recirculation to effect maximum reduction in moisture content thereof, and means for controlling the first-mentioned operation in response to temperature and the second-mentioned operation in response to a humidity condition of the air in the enclosure.

3. In air conditioning apparatus, the combination of a cooling element, means for circulating air over said cooling element for cooling and dehumidifying the same, means for recirculating a portion of the cooled and dehumidified air over the'cooling element for further dehumidifying the same, and meansresponsive to a humidity condition of air for controlling said recirculating means.

4. The combination with air conditioning apparatus comprising air cooling means, and means for conveying air in heat exchange relation with said air cooling means and delivering the same to an enclosure at a variable rate, of means for effecting operation of said apparatus at maximum rate of air delivery in response to a predetermined maximum temperature in the enclosure, means for eflecting operation of said apparatus at a reduced rate of air delivery for effecting greater dehumidification in responseto a humidity condition in the enclosure when the temperature is between said predetermined maximum temperature and a predetermined minimum temperature, and means for terminating cooling action of the apparatus in response to said predetermined minimum temperature in the enclosure.

5. The method of operating air conditioning apparatus having a cooling element for cooling and dehumidifying air for an enclosure which comprises effecting operation of the cooling element and delivering all of the cooled air to the enclosure in response to a predetermined temperature of the enclosure, and effecting operation of the cooling element and recirculating a portion of the cooled air over the cooling element for further dehumidification in response to a high humidity condition in the enclosure when the temperature is below said predetermined temperature.

6. In air conditioning apparatus for an enclosure, the combination of cooling means, means for circulating air over said cooling means, means for recirculating a portion of the air over said cooling means, a damper for controlling air flow through the last-mentioned means, means responsive to a humidity condition of the air in the enclosure for controlling said damper, and means responsive to a predetermined maximum temperature for effecting operation of the cooling means and closing said damper independently of the action of the humidity responsive means.

7. In air conditioning apparatus for an enclosure, the combination of cooling means, means for circulating air over said cooling means, means for recirculating a portion of the air over said cooling means, a damper for controlling air flow through the last-mentioned means, means responsive to a humidity condition of the air in the enclosure for controlling said cooling means and said recirculating means when the temperature in the enclosure is between predetermined upper and lower limits, means for effecting operation of the cooling means and rendering the recirculating means ineffective in response to a temperature in the enclosure abovesaid upper limit, and means for shutting off operation of the cooling means in response to a temperature below said lower limit.

8. In air conditioning apparatus, the combination of duct means, a cooling element therein, a fan for circulating air through the duct means and over the cooling element, means providing a passage from the duct means beyond the cooling element and the fan to the duct means at a point ahead of the fan and the cooling element for recirculating air for further dehumification, a damper for controlling flow through said passage, means responsive to temperature of air for controlling the operation of the cooling element,v

and means responsive to humidity of air for controlling said damper.

9. In air conditioning apparatus, the combination of duct means, a cooling element therein, a fan for circulating air through the duct means and over the cooling element, means providing a passage from the duct means beyond the cooling element and the fan to the duct means at a point ahead of the fan and the cooling element for circulating air for further dehumidification, a damper for controlling flow through said passage, means responsive to temperature of air for controlling the operation of the cooling element, and means for effecting operation of the cooling element and opening said damper in response to high humidity of air.

10. In air conditioning apparatus, thecombisage, means responsiveto a predetermined high a passage from the duct means beyond the cooling element and the fan to the duct means at a point ahead of the fan and the cooling element for circulating air for further dehumidification,

a damper for controlling flow through said passage, means responsive to a predetermined high temperature of air for effecting operation of the cooling element and closing said damper, means responsive to a predetermined low temperature of air for'shutting ofi operation of the cooling element and closing said damper, and means responsive to a temperature of air between said high and low temperatures and a high humidity of air for eflecting operation of the cooling element and opening said damper.

'1 In apparatus for supplying cooled and dehumidified air to an enclosure, the combination of a cooling element, means for conveying air in contact with the cooling element and to the enclosure, means for varying theflow of air so as to supply air from the cooling element to-the enclosure-at a relatively highrate or at a 'relatively low rate, means for supplying cooling fluid to the cooling element, humidity-responsive means for controlling the cooling fluid supply means to supply cooling fluid to the cooling element and the flow-varying means to provide a relatively low rate of air supply upon demand for dehumidiflcation, and means operable in response to a predetermined maximum temperature to control the cooling fluid supply means to supply cooling fluid to the cooling element and the flow-varying means to provide a relatively high rate of air supply independently of the action of said humidity-responsive means.

13. In air conditioning apparatus for an enclosure, the combination of means for cooling air and delivering the same to the enclosure, said cooling means being adjustable from a first con- .dition of operation to a second condition of operation to increase the ratio of latent heat re-. moval to sensible heat removal, means responsive to a high humidity and a temperature between predetermined maximum and minimum temperatures for effecting operation of said air- 

